This invention relates to deflashing articles and more particularly to apparatus for handling and segregating blow molded thermoplastic preforms wherein the thermoplastic is at elevated temperature.
U.S. Pat. No. 3,754,841 discloses forming molecularly oriented containers from blow molded preforms which have been initially shaped from a portion of an extruded hollow parison. In such system it is desirable to retain in the plastic a major part of the heat which was generated during extrusion in order that such heat can be used to provide the temperature which is necessary to produce molecular orientation and allow reshaping of the preform into a finished article in the final blow mold. Therefore, as disclosed in such patent, the preforms are ejected from the mold cavities at an overall average temperature through the wall thickness which is greater than that usually encountered in conventional blow molding where further working is not contemplated and the plastic is usually cooled to the maximum extent while in the cavity in order that it be as rigid as possible on ejection from the mold.
Inherent in practically all blow molded parts formed from a freely extruded parison is the presence of an integral neck moil which represents a short unused part of the parison length extending beyond one end of the blow mold cavity which must be removed before the article can be considered to be in final form. A "tail" portion is also formed along a thin web joint at the opposite end but this is usually broken off without much difficulty and is not of concern herein. The neck moil in the system of the aforesaid patent is desirably removed before final blowing while the plastic in the region of the integrally attached moil is at elevated temperature, since under such conditions it is more pliant than if at lower temperatures when it is quite rigid and more difficult to work. A device for sectioning articles generally found operable in this environment is typically disclosed in U.S. Pat. Nos. 3,406,598 and 3,429,211 and involves the use of a cutting blade penetrating into the object being sectioned at the desired level as it is moved across the blade between fixed and movable guides.
Sectioning articles while at elevated temperature is, however, not without problems. If the plastic is too hot it tends to stretch across the blade without any meaningful penetration through the wall at all, whereas if too low in temperature, in addition to generating wear on the cutting member, the plastic tends to crack, especially if it is brittle and has not been toughened via molecular orientation techniques. When the articles being trimmed are the aforementioned tubular preforms having body portions also at elevated temperature which have been molded with an accurate wall distribution pattern and contour related to that desired in the later formed containers, it is important to avoid or minimize contacting the plastic which will in fact form any part of the finished container prior to final molding since the plastic is hot, will readily deform to the touch and will tend to stick to an adjacent preform should it happen to strike against one during processing in a production line. Also, when such preforms are to be temperature-conditioned in an intermediate station before reshaping, it is highly desirable that they exit the neck moil trimming or deflashing station physically oriented in an attitude which will facilitate passage through such subsequent temperature-conditioning station.